Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 3choplex on July 19, 2013, 12:38:06 am
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I've been working on an old Gibson Scout lately. The other day I put in a speaker, a 12" Pyle Driver. Everything says the Scout had a 10", but the baffle is cut for a 12", shrug.
With the speaker in, the reverb is humming like crazy. I've moved the tank around, the only place I lose the noise is a couple of feet from the speaker. Is it possible to create a shielded bag or something, or am I going to need to get a different speaker with a smaller magnet? Ideas?
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Gibson Scout is a vintage amp . Why don't you keep it as most original you can ? Don't loose your time with 12 inches Pyle speaker ( are they good those speaker ? ) and trying to shield reverb tank.
Put a good 10 inches .
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I got the amp free, not working and with no speaker. The baffle was already cut for a 12", so I put in one. :)
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I got the amp free, not working and with no speaker + With the speaker in, the reverb is humming like crazy.
As stated, this is not sufficient information to conclude that the speaker is the problem.
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3choplex , are you sure you reverb tank 's wire have good shield ?
Even with a 10 inches speaker , your reverb tank wiil be too close from the magnet if you need few feet. So it is probably not the speaker's magnet your problem but a defective ground on the reverb tank or their cables .
Have you check that ?,
With no reverb tank is the amp work well ? If not fix it before go farther.
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I don't think the speaker is "the" problem. Something else is amiss like the wire shield isn't grounded or the tank isn't grounded properly. I think it's some other issue even maybe the reverb tube has gone bad?
With respect, Tubenit
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I did a little test this morning, removing the speaker. You guys are right. It's not the speaker. I'll start checking other stuff. Thanks.
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I did a little test this morning, removing the speaker. You guys are right. It's not the speaker. I'll start checking other stuff. Thanks.
+1
I was shure of that .
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I just realized I didn't give all the information in my original message. The reverb was quiet when plugged into an external cab, then when I installed the speaker in to combo cabinet I got the noise. Apparently unrelated, but that was why i was attributing it to the speaker. It was the only thing that (I was aware) had changed. Just mentioning so I don't appear crazy. :smiley:
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The reverb was quiet when plugged into an external cab, then when I installed the speaker in to combo cabinet I got the noise
Reverb cable and reverb tank look to be good so !!!
IMO , the noise have nothing to do with the reverb .
Can we just say ; the amp is noisy ( with speaker in ) ?
Ok noisy amp ;
1- more volume = more noise ?
Yes;
a) check with guitar plug in , guitare volumes to "0"
No Noise ; defective or no input shorting jack
Noise ; check tubes , ground . Some of Gibson amp don't have heater center tap ; this make noise . Make an artificial center tap with 2 X 100 ohms resistors
Do you have the schematic ?
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Gibson scout is a GA17RVT
www.gibson.com/Files/schematics/GA-17RVT%20Amp%20Scout.pdf (http://www.gibson.com/Files/schematics/GA-17RVT%20Amp%20Scout.pdf)
Schematic show there are ;
1- No heater center tap ; = noise, install 2 X 100 ohms
2- There is 2 input shorting jacks ; Check if they work , if go to ground with no guitar , contact often dirty = noise.
3- No three prong AC cord ;= caution electrical hazard and noise; Install one ,
4- Check for unmatched output tubes = noise